This invention relates generally to the aeration of waste water and more particularly to a tubular membrane diffuser equipped with an adjustable plug that permits both buoyant and non-buoyant service of the diffuser.
In the treatment of wastewater, it is common practice to provide an aeration system that includes a plurality of pipes installed in a treatment basin containing the wastewater. The piping for larger basins includes parallel air laterals that are supplied with air and in turn supply diffusers which discharge the air to the wastewater near the bottom of the basin. Different types and configurations of diffusers are used, and the different types of diffusers can discharge the air in the form of fine bubbles, medium size bubbles or coarse bubbles. The type and configuration of diffuser that is used depends upon a number of variables, including the necessary efficiency and the maintenance requirements.
The present invention is directed to an improved tubular membrane diffuser for use in a wastewater treatment system. The diffuser is characterized by a plastic pipe on which a porous membrane is sleeved in order to discharge air bubbles to the wastewater. It is a particular feature of the invention that the diffuser is equipped with an adjustable plug which can be positioned virtually anywhere along the length of the diffuser pipe between a fully buoyant position and a substantially non-buoyant position. When the diffuser is to serve in a buoyant application, the plug can be positioned at the outboard end of the diffuser pipe, and the entire length of the pipe is then filled with air. In a non-buoyant application, the plug is positioned near the inboard end of the diffuser so that most of the pipe is filled with water to counteract the buoyancy force of the air supplied to the diffuser. The plug can also be adjusted to any position along the length of the diffuser pipe for service in a partially buoyant application.
The plug is a two-piece unit which includes a ring with a tapered bore and a tapered plug element that threads into the bore. As the plug element is progressively threaded into the ring, the wedging action resulting from the mating tapers causes the ring to radially expand so that it is held tightly against the inside wall of the pipe at the desired location. The ring and plug element then seal effectively against the passage of air beyond the plug assembly.
It is an important feature of the invention that the plug is removable. This allows the plug to be adjusted in its position along the diffuser to vary the buoyancy, and it also permits the plug to be removed so that accumulated solids and other blockages can be flushed out of the end of the diffuser.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.